Stolen medical data from 500,000 NHS patients has gone up for sale on a Chinese website just a year after the Mail revealed it could be abused by Beijing for bioweapons.

There were calls for an inquiry on Thursday after it emerged that confidential NHS medical details had been offered for sale within months of Chinese researchers being granted access to the sensitive information.

Last year, there was outrage when plans emerged to give Chinese researchers access to GP records of 503,000 volunteers who are part of the UK Biobank, a research hub that makes 'de-identified' data available to universities, scientific institutes and private companies.

MPs, security experts and former spy chiefs warned against the decision, fearing the hostile state was being given a window into 'strategic aspects of the nation's life', which could be used to develop viruses and help China become a biotech superpower.

Now it's emerged that data from 500,000 UK Biobank volunteers has been offered for sale on the e-commerce site Alibaba – sometimes called China's Amazon – three times in the last week. Although the posts were removed before any sales, experts believe the reason the information is being freely touted on the site is that Beijing has already capitalised on the information.

Ian Murray, the technology minister, told MPs there had been a large-scale data breach, admitting he could not provide '100 per cent assurance' that participants could not be identified with the available data.

It came as experts revealed that it was 'the 198th known exposure of UK Biobank data since last summer'.

The stolen data did not include names, addresses, or contact details, but it did contain gender, age, month and year of birth as well as assessment centre data, attendance data, socioeconomic status and lifestyle habits.

Three Chinese research institutions have since had their access revoked after being identified as the source, having initially accessed the data legitimately.

On Thursday, shadow national security minister Alicia Kearns said Labour had handed a 'gift to China', which could endanger lives. 'Half a million Britons trusted the system with their most intimate health data. That trust has been shattered.

'Labour must now answer three questions: which institutions had their access revoked, which had links to the Chinese state, and who signed off on overriding MI5's warnings last year.'

Last April, UK Biobank announced NHS England had audited its processes for sharing data internationally, including how it assesses applications from China. It passed the audit, meaning Chinese researchers could then apply for access.

Then, in February, the health secretary Wes Streeting allowed coded GP data of all volunteers to be shared with UK Biobank.

The decision shocked security experts, with former MI6 spy chief Sir Richard Dearlove comparing it to the aborted decision to let Chinese firm Huawei have a role in the UK's 5G network. Former Tory leader Sir Iain Duncan Smith said: 'I will be calling for an inquiry into this scandal. We need to know who made this utterly stupid decision to hand China access to this medical data. It beggars belief when China is looking to develop bioweapons.'

Professor Luc Rocher from the Oxford Internet Institute said: 'This is the 198th known exposure of UK Biobank data since last summer.'

Professor Rocher added that not enough is being done to get stolen data removed from the web, saying: 'UK Biobank data is not just available for sale, it also remains available online for anyone to download today.'

Professor Sir Rory Collins, UK Biobank chief executive, said: 'We apologise to our participants for the concern this will cause.'